When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My fuel gauge was pinned past full and I tried some testing as described on this site with negative results. So, I pulled the gauge itself and i realized quickly that someone had been in there before because wires were labeled. There was a pink wire on the plug that was not connected anywhere and labeled "fused" on a piece of tape attached. Then the post on the gauge to that pink wire broke off . I was able to solder it back on and check continuity, which I had. I plugged the cable back in to the back of the fuel gauge, gave pink wire12 volts and the gauge still did not work. Is this meaning the gauge is bad?
Thank you,
Bill
My first question and im answring it my self lol....well after writting my post I realized that I had just put 12 volts to the gauge and never grounded out the trunk wire. Well, after grounding out the trunk wire my gauge went to "E" so i guess the gauge is good and sending unit bad. I still do have to get a permanent 12 volts to that pink wire off the gauge.
Just bought a 72-442 and my gas gauge is pinned past the full mark as well. In your opinion should I bother going through the wires or is the sending unit bad? This photo is better than before, it used to be pinned all the way into the "Hot" dummy light.
Last edited by 1972-442-350; December 17th, 2019 at 06:17 AM.
My car does that periodically, as did my 70 Supreme before it. On both of them it's the wire connection to the sending unit. If I reach up under the bumper near the gas filler neck and wiggle the brown wire, the gauge starts working again - until I hit a bump in the road, then it goes out again.
To test the gauge, unplug the brown wire at the connector in the trunk just before it goes through the floor pan grommet and ground the forward end against the bumper or some other metal part. If the gauge goes to E, then there is an open circuit towards the sending unit. If the gauge doesn't go to E, there's an open in the forward part of the system towards the gauge.
My first question and im answring it my self lol....well after writting my post I realized that I had just put 12 volts to the gauge and never grounded out the trunk wire. Well, after grounding out the trunk wire my gauge went to "E" so i guess the gauge is good and sending unit bad. I still do have to get a permanent 12 volts to that pink wire off the gauge.
This just happened to me after installing a new sending unit. I assumed the installation order incorrectly on these parts. Looking at build manual it's rubber ring first, sending unit next, then retaining ring. I had the sending unit, rubber ring, then retaining ring which will I believe cause the sending unit to register no resistance and therefore read E on the dial. If your dial read full and beyond "F" when you unplugged the tan wire where the trunk grommet is, then your gauge is in good working order. If when you reconnect the tan wire to the trunk harness and the gauge goes to "E" then something is grounding the sending unit before the resistor the floating swing arm attaches to.
Last edited by EdwardB; December 17th, 2019 at 02:01 PM.
If you get your sending unit out you can bench test it with an Ohm meter. Range should be from 0 to 90 or so. Just hook one lead from the meter to the sending unit ground and the other lead where the tan wire would normally be and move the arm back and forth. Empty is 0 Ohms and full is around 90 Ohms. Hope that helps you. Be sure to use a brass punch to remove the retaining ring so you don't blow yourself up. (Brass won't spark) You may only need a new sending rubber ring seal. 99 cents
Last edited by EdwardB; December 17th, 2019 at 01:54 PM.
The gas gauge seems to have corrected itself? Could have been stuck because before I recently bought it, it sat for years with only an occasional start up. The weather isn't permitting me to drive it around much for testing so we'll see if it acts up through time. So far I've gotten lucky and it's working...we'll see.
The gas gauge seems to have corrected itself? Could have been stuck because before I recently bought it, it sat for years with only an occasional start up. The weather isn't permitting me to drive it around much for testing so we'll see if it acts up through time. So far I've gotten lucky and it's working...we'll see.
Sounds familiar. As I posted above, mine comes and goes as I drive due to a loose wire connection at the sending unit. Hit a bump and it changes state.
So I took my tank out and corrected the sequence on the sending unit this week (rubber ring, sending unit, retainer ring) and guess what. I have a working gas gauge now.
I have a question regarding the gas gauge in my 1965 Cutlass. The gas gauge works but with about 6 gallons of gas in the tank the needle sits squarely on the empty mark. I can attach a sending unit outside the tank and move the float rod back and forth and the gauge moves accordingly. I put a new sending unit in, and that didn't help. I will add another 5 gallons to the tank and see what happens. I have checked the grounds, wiring , battery voltage, etc. I know gas gauges are odd when it comes to relationship to what the needle says and what is really in the tank, but would it by typical for the gauge to show empty and still have 5 or 6 gallons in the take. Or did they figure drivers would procrastinate so they scare you into going to the gas station early??
Last edited by jRoofgunner; February 2nd, 2020 at 01:15 PM.
Reason: word correction
I did this after watching a video and it worked. Friends complained that using an aftermarket sending unit always threw off their real fuel reading. Take your tank out and remove your sending unit. Then measure from the hole where the sending unit is straight down to the bottom of the tank. Should be about 8 inches. Look at the swing arc of your float. The top to bottom distance of the swing you currently have is probably only about 5 to 6 inches (the y axis-straight up and down). Bend the metal arm so that you have enough length to almost reach the bottom of your tank based off of your tank measurement depth. Reinstall and your gauge will be more accurate. Also while your sending unit is out test it with an Ohm meter. Full setting should register around 90 Ohms or so, empty should be 0 Ohms. Sorry you will have to remove your tank but it pays off having an accurate reading. It also is possible to knock your float off using a siphon-been there-done that
Last edited by EdwardB; February 2nd, 2020 at 01:48 PM.
I checked all that you mentioned regarding the sending units and bent the float rods. I lined up the three sending units. I had one original out of the 65 Cutlass. It bounced the Ohm meter all over the place while the other two gave consistent readings. I checked grounds, connections, etc. The two good units operated the gauge correctly outside of the tank. I put one in(new one) with the float resting on the bottom of the tank, put the 6.5 gallons in and the gauge rested squarely on the "E". The tank is a 20 gal. tank. With this the Ohm meter showed about 11 Ohms. It needed to show about 30 Ohms or about 1 inch raise of the float to show the correct fuel level. So I installed a variable resistor capable of 2-120 ohms. in the sending unit circuit which registered 1/3 tank; the resistor set to about 25ohms. While I was doing this, I removed the float from the Original sending unit and the one from the other NEW sending unit I had obtained from OPGI (I think it was a Spectra Premium). I weighed them on my reloading scale. The original one weighed about 95 grains. The new one was about 136 grains. That is the difference in the weight of a .22 cal 40 grain bullet. My guess is that between that weight and the possibility todays fuel has less specific gravity compared to the leaded gas would result in a one inch less raise of the arm or so hence the sending unit won't give the gauge the correct ohms.
November 25th, 2019, 12:51 PM
